1. Field of the Invention
The present invention relates to an image sensor having a light-sensitive surface, nonlight-sensitive circuit section, and a wiring section for connecting the circuit section, and wiring section.
2. Discussion of the Background Information
To record still or moving images in video technology, two main methods have become established in the past few years, photodiode arrays and CCD sensors. Currently, over 90% of all sensors that are used are CCD technology.
The photodiode array is the older technology, but in its original form it had several technologically-caused disadvantages that led to lower sensitivity, higher noises, lower speed, etc., which is why it has been displaced by the CCD sensors for the most part.
However, CCD sensors have the disadvantage that, due to the additional complexity of the manufacturing process and the increased manufacturing costs, they cannot easily be integrated with CMOS circuits. In addition, CCD sensors are high-capacity devices, so that on-chip CMOS driver electronics for large-surface assemblies would require very high power (2 to 3 W). Moreover, many different voltage levels are required for CCD sensors in order to ensure high efficiency of the charge transfer.
In contrast, progress in silicon technology has made it possible, in a photodiode array, to add a separate active processing unit (e.g., amplifier, etc.) to each image recording member, thereby eliminating the existing disadvantages of the photodiode arrays and, in particular, even creating new capabilities for image recording. This is known as xe2x80x9cAPSxe2x80x9d (xe2x80x9cactive pixel sensorxe2x80x9d) technology. APS technology is currently considered to be very significant technologically for the future.
Improvements have been made to the known systems to increase image sharpness and resolution so that a sharp image with good resolution and high contrast can be represented with a predetermined number of image members. In that regard, it has been observed that a hexagonal arrangement of sexangular members, as also present in the retina of humans and animals, is also very advantageous. However, such an arrangement is linked to the problem that digital image processing is obviously hampered, because the individual image sensor members are not arranged in an assembly of columns and rows.
However, with regard to optimizing the assembly of image sensor members, the known CCD sensors have the disadvantage that CCD technology offers very little freedom with regard to the shape and arrangement of the pixels. In practice, only rectangular shapes of image sensor members, which are combined into a regular Cartesian matrix, are of importance.
In U.S. Pat. No. 3,971,065, an image sensor is described in which three different types of image sensor members, each consisting of CCD sensors, are arranged in such a way that the same types of image sensor members are arranged in the form of grids. More specifically, the various types of image sensor members each represent a first color, for example, green, a second color, for example, red, and the general brightness. The image sensor members for general brightness are disposed in a checkerboard pattern, while the image sensor members for the first color fill up the intermediate spaces in a first checkerboard pattern row, the image sensor members for the second color fill up the intermediate spaces in the second checkerboard pattern row, and so on. This is intended, on the one hand, to avoid the high complexity of the optical design and, on the other hand, to avoid the problems related to the conventional process of image position accuracy when using filters for different colors disposed behind one another.
Compared to the CCD sensors, when using APS-CMOS sensors in principle almost any chosen form with any chosen overall arrangement is feasible.
In a known AP sensor, as known, for example, from xe2x80x9cCMOS Active Pixel Image Sensors for Highly Integrated Imaging Systems,xe2x80x9d Sunetra K. Mendis et al., IEEE Journal of Solid-State Circuits, Vol. 32 No. Feb. 2, 1997, or xe2x80x9cSmar Image Sensors for Optical Microsystems,xe2x80x9d Peter Seitz, et al., Laser und Optoelectronik 28(6)/1996, an individual sensor member substantially comprises three components, which are disposed as shown in FIG. 4a: 
1. A light-sensitive surface 101 in the form of a photodiode or a phototransistor
2. A circuit section 100 which, for example, includes multiple CMOS transistors and is generally not used for light sensors, to generate a signal corresponding to the incident light and processing of the signal
3. A wiring section 102 which connects the individual sensor image members to an overall sensor
The arrangement of the components of the individual sensor members is determined according to switching and layout requirements and is not necessarily optimal for later additional processing of the image information. The sensor members are then arranged according to FIG. 4b into a matrix or other structures.
When optimizing the known image sensor members and image sensors, one skilled in the art will find himself in the field of tension of the following contradictory trends.
1. On the one hand, image sharpness and resolution can be improved by increasing the number of image sensors and enlarging the ratio of light-sensitive surface to image sensor surface.
2. On the other hand, the cost and speed of the resulting image sensor depend on the number of sensor members. In other words, the greater the number of sensor members, the slower and more expensive the resulting image sensor becomes.
An aspect of the present invention is therefore to improve the known image sensor member and the known assembly of image sensor members in such a way that the costs of the image sensor resulting from the image sensor members is reduced, its speed is increased, and, simultaneously, the image sharpness and resolution of the image sensor are not impaired.
According to an aspect of the present invention, an assembly of image sensor members is provided for line or column-wise recording of images, each having a light-sensitive surface; and a circuit section which in addition has a wiring section for connecting the individual circuit sections to one another and to the outside, in which the circuit section and the wiring section each occupy one part of the surface of the image sensor member characterized in that each center of gravity (centerpoints) of the light-sensitive surfaces of the individual image sensor members is disposed in the form of at least two square grids which are offset relative to one another, while the lines of the square grids are each parallel to the lines or columns of the image to be recorded.
According to a further aspect of the present invention, an assembly of image sensors members is provided wherein the light sensitive surface is disposed on one half of the image sensor member. According to a still further aspect of the present invention, the image sensors are used in a high-speed camera.
According to an aspect of the present invention, a rectangular image sensor member with a predetermined length and width is provided, the rectangular image sensor member including a light sensitive surface; a circuit section; a wiring section for connecting said circuit section to an external circuit; a first surface portion in which the circuit section and wiring section are arranged; and the light sensitive surface being arranged outside of said first surface portion.
According to another aspect of the present invention, the light-sensitive surface substantially covers the predetermined width. Additionally, other aspects of the present invention includes an image sensor member having a length to width ratio of about 2:1, 3:1, or 4:1. In another aspect of the present invention the light-sensitive surface is formed as one of a square, rectangle, hexagon, and circle.
According to a further aspect of the present invention, the light-sensitive surface is disposed on about one half of the image sensor member. In another aspect of the present invention, the light-sensitive surface is a photodiode, phototransistor, or photoresistor.
According to still a further aspect of the present invention, an apparatus is provided including a plurality of rectangular image sensor members, each rectangular image sensor member having a predetermined length and width, and ftirther including a light-sensitive surface having a centerpoint; a circuit section; a wiring section for connecting said circuit section to an external circuit; a first portion in which the circuit section and wiring section are positioned; the light sensitive surface being located outside of said first portion; the plurality of rectangular image sensor members being arranged into a plurality of rows, wherein the center point of the light sensitive surfaces of one row are positionally offset from the center point of the light sensitive surfaces of an adjacent row.
In another aspect of the present invention, row includes a plurality of members positioned to each other so that the predetermined widths of the members are vertically oriented and contiguous and the predetermined lengths of the member are horizontally oriented and aligned in a substantially parallel manner; wherein each row is configured so that the vertically oriented widths of said members with respect to a row above and row below a middle row, are offset from the vertically oriented width sides of each member of said middle row; and wherein said centerpoints of each light-sensitive surface are separated by a circuit section with respect to the rows and with respect to a vertical direction.
According to still a further aspect of the present invention the centerpoints in adjacent rows are positionally offset with respect to direction cross-wise to the rows. Further aspects of the invention include arranging the light-sensitive surface and at least a part of the first portion of a same image sensor member are arranged in a same row.
According to another aspect of the present invention, the rectangular image sensor members are arranged in a checkerboard pattern so that the light-sensitive surfaces are disposed between the circuit sections in horizontal and vertical directions and comers of the light-sensitive surfaces are contiguous in diagonal directions. According to a further aspect of the present invention, the light-sensitive surface substantially covers an entire width of the member.
According to an aspect of the present invention, the member has a length to width ratio of one of 2:1, 3:1, or 4:1. According to another aspect of the present invention, the light-sensitive surface is formed as a square, rectangle, hexagon, or circle. According to another aspect of the invention, the light-sensitive surface is disposed on about one half of said image sensor member.
According to another aspect of the present invention, the light-sensitive surface is a photodiode, phototransistor, and photoresistor. Additionally, other aspects of the present invention include the apparatus in combination with a high-speed camera.
In another aspect of the present invention, the apparatus includes wiring members connecting the wiring sections of the image sensor members to the circuit outside said image sensor member; and a calculation unit, connected to the wiring members, for interpolation of data obtained from the apparatus.
According to a further aspect of the present invention the centerpoints of image sensor members positioned in the row above and row below are aligned in a horizontal and vertical direction; and the centerpoints of image sensor members positioned in the middle row, are offset by half the distance between the distance between the centerpoints from the row above and row below, in a horizontal and vertical direction.
According to a further aspect of the invention, with respect to said cross-wise direction to the rows, centerpoints in adjacent rows are not aligned with each other. According to still a further aspect of the present invention, wherein the centerpoints of the one row are positioned substantially at a midpoint between adjacent centerpoints of the adjacent row.
In another aspect of the present invention, the external circuit includes a calculation unit adapted for interpolation of data, and the apparatus including wiring members arranged to connect the wiring sections to the calculation unit. Further aspects of the invention includes a spacing distance between adjacent centerpoints in each row is substantially the same, and wherein centerpoints in the one row are arranged at one-half of the spacing distance of the adjacent row.
The present invention is essentially based on the realization that the perfornance of an image sensor can be improved by disposing the centers of gravity (centerpoint) of the light-sensitive surfaces of the individual image sensor members in the form of at least two square grids which are offset relative to one another, with the lines of the square grids each being parallel to the lines or columns of the image to be recorded.
In that regard, the centers of gravity (centerpoint) of the light-sensitive areas of the individual image sensor members are preferably disposed in a grid line in such a way that they fall on half of the distance between two centers of gravity of light-sensitive surfaces of the individual image sensor members of the preceding grid line, as shown in FIG. 5. According to a particularly preferred embodiment, a type of checkerboard pattern is produced, as shown in FIG. 2. The image information of the areas of each image sensor member lying between the light-sensitive surfaces can then be obtained by known interpolation processes, as known, for example, from the contribution by Kris S. Balch, xe2x80x9cReplacing 16 mm Film Cameras with High Definition Digital Camerasxe2x80x9d in xe2x80x9cUltrahigh-and High-Speed Photography, Videography, and Photonics ""94,xe2x80x9d Proceedings of SPIE xe2x80x94The International Society for Optical Engineering, Jul. 27-28, 1994, Vol. 2273.
In that regard, such a grid can advantageously be produced by assigning individual image sensor members, which are designed as defined in claim 1, to a sensor of any chosen size.
Therefore, the fact that, in a known CMOS sensor in APS technology, only one portion of the sensor surface is available for light sensors is deliberately used in the present invention by disposing light-sensitive and non-light-sensitive parts in such a way that an image can be reconstructed using interpolation processes which is of higher quality than an image having the same number of image sensor members but another shape and assembly of image sensor members. According to the present invention, known interpolation processes can be used for interpolation.
The interpolation process can be implemented directly into the hardware so that the interpolation process is not time-critical, i.e., does not cause a delay in the image recording process. In addition, the interpolation process can be shifted back in time, so that it takes place not during image recording but rather not until image processing.
The calculation unit for interpolation of the obtained data can also be contained in the circuit section of each individual image sensor member.
According to the present invention, the following advantages are achieved:
1. The technological background condition that the entire image sensor member surface is not available for the light-sensitive members or surfaces (filling factor  less than  less than 100%, because the switching in each image sensor member requires space) is deliberately used. Structures are produced that allow the use of simpler, very effective interpolation processes. The effectiveness of those interpolation processes is due to the fact that the entire sensor surface or image sensor member surface is not occupied by light-sensitive members, but rather that light-sensitive and non-light-sensitive regions are disposed appropriately.
2. The simplest conversion of the obtained pixels into an image format in the form of a regular Cartesian matrix for further use in image processing. The xe2x80x9cblank fieldsxe2x80x9d of the checkerboard structure can easily be obtained by interpolation, thereby providing an image with square pixels.
3. Because, due to the device according to the invention, effectively fewer pixels are required in the image sensor for an image of equivalent quality, faster and more cost-effective cameras can be achieved.